1. Field of the Invention
This invention relates to the polymerization of cyclic poly(aryl ether) oligomers. More particularly, this invention relates to methods for the preparation of poly(aryl ethers) from cyclic poly(aryl ether) oligomers, and especially to the preparation therefrom of composites containing reinforcing materials through ring opening polymerizations.
Low melt viscosity cyclic oligomers may be catalytically converted to high molecular weight poly(aryl ethers) which are noted for high temperature stability and solvent resistance. These cyclic oligomers are useful for preparing shaped articles where the high melt viscosities typical of high molecular weight linear poly(aryl ethers) are undesirable.
The use of thermoplastic resins to prepare composites has received considerable attention in recent years. An important advantage of thermoplastic composites relative to those based on thermosets is excellent retention of mechanical properties after impact.
An important disadvantage of thermoplastic composites is the cost of manufacture of small numbers of finished parts. Molds and autoclaves suitable for the high temperature and pressure required are expensive. In addition, the high melt viscosity of thermoplastics causes considerable difficulties in the coating of fibers without the formation of voids, which are detrimental to the mechanical properties of the composite.
One solution to this problem is to prepare a cyclic precursor which ring opens upon heating. Ring opening polymerizations are desirable for this application in that there are no coproducts which must be removed.
2. Description of Related Art
An example well known in the art of the use of a cyclic precursor which ring opens upon heating in the presence of a catalyst is that of caprolactam. In this application caprolactam is used as a low viscosity monomer for the preparation of nylon 6, an aliphatic polyamide. A second example, described by Burnelle, et al., in U.S. Pat No. 4,644,053 (1987) is the polymerization of cyclic carbonates of Bisphenol A, (2,2'-bis(4-hydroxyphenyl)propane).
A consideration for many composite applications is that they need resistance to high temperatures, humid environments, and chemicals such as fuels, hydraulic fluids, and cleaning solvents. The aforementioned aliphatic polyamide and Bisphenol A polycarbonate do not have the necessary combination of properties. Poly(aryl ethers) are an important class of thermoplastic resins employed for the manufacture of composites which do meet the above requirements. Therefore, low viscosity precursors to poly(aryl ether) thermoplastics are highly desirable for the manufacture of composites. The Applicants have developed a general method and several specific methods for the preparation of cyclic poly aryl ether) oligomers, which are described in the Applicant's copending application titled "Cyclic Poly(Aryl Ether) Oligomers", which is hereby incorporated by reference.
There are numerous examples in the prior art of the preparation of poly (aryl ethers) and related polymers, usually with the aid of a polymerization catalyst such as an alkali metal halide or carbonate, including U.S. Pat. No.'s 3,441,538, 3,941,748, 4,169,178, 4,320,224, 4,638,044, 4,687,833, 4,731,429, 4,748,227, and 4,767,838. In U.S. Pat. No. 4,360,630, this type of polymer was used to prepare composites. EP 317,226 discloses macrocyclic compounds, including cyclic ethers, containing polyarylene units and other cyclic units, and the polymerization thereof. WO 88/06605 discloses random macrocyclic monomer and oligomer compounds containing a spiro(bis)indane moiety.